Hydraulic control arrangement

Abstract

A hydraulic control arrangement for height regulation of an agricultural vehicle has a control valve with a control slider provided with a first piston portion with a control edge and a second piston portion with a throttle point. In the positions of neutral and lifting of the control slider the control edge blocks the communication from a control chamber to a working chamber which is connected with a spring chamber of a throttle valve. In the position of lifting the control edge opens and the pressure medium flows via the throttle point from the working chamber in the control chamber. Thereby the pressure in the spring chamber of the throttle valve is lifted. Therefore a lower neutral circulating pressure and a higher pressure level in the position of lifting is possible.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims. 
     
       1. A hydraulic control arrangement for a working device which is driven by a single acting hydromotor and arranged particularly on an agricultural vehicle, the control arrangement comprising a pressure medium source; a throttle valve, a control valve and a blocking unit located in three planes, said control valve having a control slider having a first control edge which controls a pressure medium stream flowing to the hydromotor during lifting, and a second edge which controls the pressure medium stream flowing from the hydromotor during lowering; a working conduit extending from said pressure medium source via said first control edge of said control slider to the hydromotor; a spring-loaded throttle slider arranged before said control slider in said working conduit and providing a load-sensing control; a spring chamber associated with said throttle slider; a third control edge which in the positions of neutral and of lowering of said control slider separates said spring chamber from said working conduit; a fourth control edge which in the position of lifting communicates said spring chamber with said working conduit via a throttle point; a plurality of chambers associated with said control slider and including first and second control chambers, first and second working chambers, said control slider having a first piston portion provided with in annular groove, said third and fourth control edges being formed on said first piston portion and separated by said annular groove, said piston portion controlling a communication from said second working chamber, said blocking unit having a blocking valve; and a first control conduit, said working conduit extending from said first control chamber to said blocking valve, said second working chamber being connected via said first control conduit with said spring chamber of said throttle slider. 
     
     
       2. A control arrangement as defined in claim 1; and further comprising first and second return chambers associated with said control slider, said control slider having a second piston portion with a negative switching overlap between said second working chamber, said second control chamber and said second return chamber. 
     
     
       3. A control arrangement as defined in claim 2, wherein said second control chamber in the position of lifting of said control slider is separated from said second working chamber by said second piston portion with negative switching overlap. 
     
     
       4. A control arrangement as defined in claim 2, wherein said second control chamber in the position of lowering of said control slider is blocked from said second return chamber by said second piston portion with negative switching overlap. 
     
     
       5. A control arrangement as defined in claim 1, wherein said blocking unit is arranged in said working conduit between said control slider and the hydromotor; and further comprising a second control conduit extending from said second control chamber and having a pressure controlling said blocking unit. 
     
     
       6. A control arrangement as defined in claim 5, wherein said second control conduit is provided with a throttle point. 
     
     
       7. A control arrangement as defined in claim 5, wherein said second control conduit is provided with a pressure maintaining valve. 
     
     
       8. A control arrangement as defined in claim 1, wherein said throttle valve is a three-way throttle valve, said throttle slider being a part of said three-way throttle valve and having two further control edges. 
     
     
       9. A hydraulic control arrangement for a working device which is driven by a single-acting hydromotor and arranged particularly on an agricultural vehicle, the control arrangement comprising a pressure medium source; a control slider having a first control edge which controls a pressure medium stream flowing to the hydromotor during lifting, and a second control edge which controls the pressure medium stream flowing from the hydromotor during lowering; a working conduit extending from said pressure medium source via said first control edge of said control slider to the hydromotor; a spring-loaded throttle slider arranged before said control slider in said working conduit and providing a loadsensing control; a third control edge which in the positions of neutral and of lowering of said control slider separates said spring chamber from said working conduit; and a fourth control edge which in the position of lifting communicates said spring chamber with said working conduit via a throttle point; a compensating passage with a further throttle point therein; a check valve which opens in said compensating passage; a plurality of chambers associated with said control slider and including first and second control chambers and damping chambers, said damping chambers being connected with one another by said compensating passage with said further throttle point, said second control chamber being connected with said compensating passage by said check valve.